But... you could probably take pictures of the currency using Google Goggles, and then look at the corresponding search results in Google to help figure out the value/currency identification.
edit: Just tried it on the following bills/bank notes:
- 1000 Ruble (Russia) note
- 500 Ruble note
- Really beat up 10 ruble note
- 10 Euro note
- 20 Euro note
- 100 dollar bill (US)
The ruble notes returned searches for "rubles" and "Russian," but no exact denominations. The euros in all pictures returned searches for the exact denomination and identification of the note (10 Euro, 20 Euro). The 100 dollar bill also returned a correct identification and denomination.
I'm guessing you probably wouldn't have the best of luck with less common currencies. The euro and the dollar are without a doubt the world's biggest currencies. So it only makes sense that they worked just fine in Google Goggles. I was surprised that the rubles were correctly identified as such in some of the searches. At least it got the language correct, so you could figure out the currency based on that.
If using this technique, just make sure that the bill or bank note is properly in focus, otherwise it'll definitely return "no results."
edit2: Just out of curiosity, I tried Google Goggles on a bunch of euro coins I had laying around. Unfortunately, I couldn't get a good enough shot out of any of them for Google Goggles. Nuts.